Refillable beverage containers, such as commuter coffee mugs, for example, typically include a removable lid that includes a fluid aperture, and a user typically fills the interior of the container (e.g., an insulated container) with a beverage (e.g., coffee) when the lid is removed. To drink the beverage, the user typically tips the container to allow the beverage to pass through the fluid aperture, and the user sips the beverage as the beverage exits the fluid aperture. Because the beverage may be very hot, it is desired to prevent the beverage from spilling out of the fluid aperture if the container is accidentally tipped. Accordingly, refillable beverage containers can include a selective locking device on the lid that allows fluid to pass through the fluid aperture only when the locking device is in a desired position. A typical locking mechanism includes a lever or button that is displaced by the user prior to (or while) sipping the beverage. However, if such a refillable beverage container is carried in a bag with other items, contact between the items within the bag and the lever or button may accidentally disengage the locking mechanism and cause the beverage to pass through the fluid aperture and onto the items in the bag. Moreover, typical refillable beverage containers have a drinking area adjacent to or surrounding the fluid aperture that can become dirty with contact from the debris within the bag. Consequently, there is a need for a removable lid having a locking mechanism that cannot be accidentally depressed and that is easy to lock and unlock. There is also a need for a cover to protect the fluid aperture when the refillable beverage container is stored but that allows access to the fluid aperture when the user desires to drink the beverage.